it's NEVER good (or proper) to end a sentence with a preposition. Simply put, it's poor grammar.

I disagree. There are many times when it is correct to end a sentance with a preposition. Take the sentance "What did you step on?" Sure you could say On what did you step, but that is not how people really talk. It is much more awkward to say it that way than to end with a prepositon.

Winston Churchill had a famous response when someone told him the "rule" about ending a sentance with a preposition. He said "That is a rule up with which I will not put."